Ukraine handed over 222 prisoners and the rebels released 145 people, according to Russia's state RIA Novosti news agency — the biggest one-time prisoners swap since the pro-Russian insurgency flared up in eastern Ukraine in April.

The Interfax news agency quoted Svyatoslav Tsegolko, a spokesman for Ukrainian President Petro Poroshenko, saying that 146 Ukrainian prisoners were released Friday and another four will be freed on Saturday. The figures corresponded to an earlier Ukrainian official statement, which said that 150 Ukrainian prisoners were to be released.

Hundreds of others were released during previous months.

Numbers of those to be released varied Friday and tensions were flying high as buses carrying the prisoners arrived at a site north of the main rebel stronghold of Donetsk.

At some point during the exchange, separatist rights ombudsman Darya Morozova was quoted by Tass news agency as saying that the exchange was pushed back until Saturday.

Russia's state television showed Ukrainian war prisoners boarding buses in the main rebel stronghold of Donetsk before being driven to a location north of the city where the exchange took place.

On the site where the swap was conducted, prisoners were called up by groups of 10 with officials from both sides verifying their identities.

The exchange had been tentatively planned for earlier this week, and the failure to conduct it pushed back another round of Ukraine peace talks in the Belarusian capital, Minsk, which was set for Friday but was adjourned indefinitely.

Fighting in eastern Ukraine between government forces, volunteer battalions and pro-Russia separatists has claimed more than 4,700 lives since last spring.

Previous rounds of talks in September produced a cease-fire and an agreement to pull back heavy weapons, but both sides have failed to agree on a line of division and fighting continued.

Hostilities have diminished in the past weeks amid renewed peace efforts, but mutual suspicions and distrust have stymied progress.

Ukraine's parliament vote earlier this week to abandon the country's non-aligned status, a first step toward a possible bid for NATO membership which is an anathema to Moscow, also has hampered talks.

Amid the tensions, Ukraine on Friday suspended train and bus services to the Russia-annexed Crimean Peninsula, citing security concerns. Crimea, which depends on Ukraine for supplies of electricity and water, has faced frequent power cutoffs, most recently on Friday.

Russia annexed the Black Sea peninsula in March following the ouster of Ukraine's former Moscow-friendly president after months of protests.

Adding to the residents' problems, Visa and MasterCard announced Friday that they halted card services in Crimea in line with the latest U.S. sanctions.